The last option.
The first one is wrong because Elmer is a new subject and thus makes this a compound sentence. Due to that, there should be a comma before and.
The second is wrong because there is no new subject after “and”. There is simply a new verb, which means there shouldn’t be that comma
The third is wrong because there is no verb between Margarita and the comma to justify the comma. It should be “Margarite and Elmer attended…”
Thus, by deduction, the fourth answer is right